Allow supply chains to overlap!

1 files changed, 93 insertions, 60 deletions

diff --git a/rules.js b/rules.js
index 9035336..7481754 100644
--- a/rules.js
+++ b/rules.js
@@ -53,6 +53,63 @@ function debug_hexes(n, list) {
 		console.log("".padStart(y," ") + list.slice(y*hexw, (y+1)*hexw).map(x=>String(x).padStart(2, ' ')).join(""))
 }
 
+// === CRC32 CHECKSUM ===
+
+const CRC32C_TABLE = new Int32Array([
+	0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
+	0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b, 0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
+	0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
+	0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
+	0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a, 0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
+	0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
+	0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
+	0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a, 0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
+	0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
+	0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
+	0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927, 0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
+	0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
+	0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789,
+	0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859, 0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46,
+	0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
+	0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829,
+	0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c, 0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93,
+	0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
+	0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc,
+	0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c, 0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033,
+	0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
+	0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982,
+	0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d, 0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622,
+	0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
+	0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f,
+	0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
+	0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
+	0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f,
+	0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee, 0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1,
+	0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
+	0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e,
+	0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e, 0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351
+])
+
+// fast with unlikely collisions
+function supply_memo_idx_crc32c(data, tail1, tail2) {
+	var x = 0
+	for (var i = 0, n = data.length; i < n; ++i)
+		x = CRC32C_TABLE[(x ^ data[i]) & 0xff] ^ (x >>> 8)
+	x = CRC32C_TABLE[(x ^ tail1) & 0xff] ^ (x >>> 8)
+	x = CRC32C_TABLE[(x ^ tail2) & 0xff] ^ (x >>> 8)
+	return x
+}
+
+// slow but guaranteed no collisions
+function supply_memo_idx_slow(data, tail1, tail2) {
+	var x = 0n
+	for (var i = 0, n = data.length; i < n; ++i)
+		x = (x << 8n) | BigInt(data[i])
+	x = (x << 8n) | BigInt(tail1)
+	x = (x << 8n) | BigInt(tail2)
+	return x
+}
+
 // === CONSTS ===
 
 const AXIS = 'Axis'
@@ -1142,7 +1199,7 @@ function shuffle_cards() {
 
 var supply_friendly_hexes, supply_friendly_sides, supply_friendly, supply_enemy, supply_net, supply_line
 var supply_visited = new Array(hexcount).fill(0)
-var supply_memo = new Array(hexcount * 8 * 6).fill(0)
+var supply_memo = new Set()
 
 // PASS 1: Forward scan from source to compute potential supply net and valid hex side crossings.
 // Simple uniform cost search.
@@ -1256,7 +1313,7 @@ function trace_supply_network_1(start)
 			supply_visited[next] = next_move
 
 			if (supply_friendly[next] > 0 && !supply_net[next])
-				search_order.unshift(next)
+				search_order.push(next)
 
 			supply_net[next] = 1
 
@@ -1335,27 +1392,38 @@ function backward_supply_next_move_type(here_move, road) {
 	return BACK_ABORT
 }
 
-function trace_unit_supply_line(path, here, here_move, ssrc, from_dir) {
-	let memo_idx = here * 48 + here_move * 6 + from_dir
-	if (supply_memo[memo_idx]) {
-		for (let x of path)
-			supply_line[x] = 2
+function path_includes(list, x) {
+	for (var i = list.length - 1; i >= 0; --i)
+		if (list[i] === x)
+			return true
+	return false
+}
+
+function trace_unit_supply_line(full_path, path, here, here_move, ssrc, from_dir) {
+	// CORRECT (but slow): let memo_idx = supply_memo_idx_slow(full_path, here, here_move * 6 + from_dir)
+	// CRC32-C we pray for no collisions!
+	let memo_idx = supply_memo_idx_crc32c(full_path, here, here_move * 6 + from_dir)
+	if (supply_memo.has(memo_idx)) {
 		return true
 	}
 
-	supply_visited[here] = 1
+	path.push(here)
+	if (supply_friendly[here] > 1)
+		full_path.push(here)
+
 	let supplied = false
 
 	for (let s = 0; s < 6; ++s) {
 		let next = here + hexnext[s]
 
-
 		// can't go off-map
 		if (next < first_hex || next > last_hex)
 			continue
 
 		// already seen
-		if (supply_visited[next])
+		if (path_includes(full_path, next)) // supply chain - heads (can't loop back)
+			continue
+		if (path_includes(path, next)) // supply chain - intermediate links (can't double back from _same_ head)
 			continue
 
 		// not part of supply network (from pass 1)
@@ -1371,43 +1439,10 @@ function trace_unit_supply_line(path, here, here_move, ssrc, from_dir) {
 		if (next_move === TRACE_ABORT)
 			continue
 
-		let reached = (next === ssrc)
-		if (!reached) {
-			// Sometimes we can stop searching if we reach a supplied highway.
-			if (hex_road[next] === HIGHWAY && supply_net[next] === 2) {
-
-				// But only if we can't continue by trail or track.
-				// If we always stop we'll miss possible departures that reconnect
-				// to the highway elsewhere.
-				//
-				// Example: Tobruk - EL Adem - Sidi Rezegh - Ft. Capuzzo
-
-				// Not enough movement left to leave highway:
-				if (next_move === BACK_HIGHWAY_3 || next_move === BACK_STOP)
-					reached = true
-
-				// MAYBE WRONG
-				// (can we leave supplied highway to connect to chain elsewhere?)
-				// Only these places can reconnect to the highway using trail/track:
-				if (
-					next !== 35 && // Gazala
-					next !== 55 && // Er Regima
-					next !== 61 && // Bir Harmat
-					next !== 62 && // El Adem
-					next !== 64 && // Ft. Capuzzo
-					next !== 65 && // Sollum
-					next !== 78 // Ghemines
-				)
-					reached = true
-			}
-		}
-
 		// reached supply source
-		if (reached) {
-			for (let x of path)
-				supply_line[x] = 2
-			supply_line[side] = 2
+		if (next === ssrc) {
 			supply_net[next] = 2
+			supply_line[side] = 2
 			supplied = true
 			continue
 		}
@@ -1420,16 +1455,19 @@ function trace_unit_supply_line(path, here, here_move, ssrc, from_dir) {
 		if (next_move === BACK_STOP && hex_road[next] === HIGHWAY)
 			next_move = BACK_HIGHWAY_3
 
-		path.push(side)
-		if (trace_unit_supply_line(path, next, next_move, ssrc, s))
+		if (trace_unit_supply_line(full_path, supply_friendly[next] > 1 ? [] : path, next, next_move, ssrc, s)) {
+			supply_line[side] = 2
 			supplied = true
-		path.pop()
+		}
 	}
-	supply_visited[here] = 0
+
+	path.pop()
+	if (supply_friendly[here] > 1)
+		full_path.pop()
 
 	if (supplied) {
 		supply_net[here] = 2
-		supply_memo[memo_idx] = 1
+		supply_memo.add(memo_idx)
 	}
 
 	return supplied
@@ -1462,12 +1500,10 @@ function trace_supply_network(start) {
 	let search_order = trace_supply_network_1(start)
 
 	// Pass 2: Filter hexes that have actual supply lines from units.
-	supply_visited.fill(0)
-	supply_memo.fill(0)
-	let path = []
+	supply_memo.clear()
 	for (let x of search_order) {
 		if (supply_friendly[x] > 0 && x !== start) {
-			trace_unit_supply_line(path, x, BACK_HEAD, start, 0)
+			trace_unit_supply_line([], [], x, BACK_HEAD, start, 0)
 		}
 	}
 
@@ -1489,15 +1525,12 @@ function trace_fortress_network(fortress, ss) {
 	trace_supply_network_1(fortress)
 
 	// Pass 2: Filter hexes that have actual supply lines from units.
-	supply_visited.fill(0)
-	supply_memo.fill(0)
-	let path = []
+	supply_memo.clear()
 	for (let u = 0; u < unit_count; ++u) {
 		if (unit_supply(u) === ss) {
 			let x = unit_hex(u)
 			if (is_map_hex(x) && x !== fortress) {
-				//if (supply_friendly[x] > 1 && supply_net[x]) continue
-				trace_unit_supply_line(path, x, BACK_HEAD, fortress, 0)
+				trace_unit_supply_line([], [], x, BACK_HEAD, fortress, 0)
 			}
 		}
 	}
@@ -3161,7 +3194,7 @@ function save_withdrawal_supply_lines() {
 	}
 }
 
-// ==== MOVEMENT PHASE ===
+// === MOVEMENT PHASE ===
 
 function push_move_summary(from, to, via, forced) {
 	let mm = (from) | (to << 8) | (via << 16) | (forced << 24)